The present invention relates to levellers, a device typically attached to tractors, excavators, and skid-steer vehicles for the purpose of levelling and smoothing the ground. It is envisaged however that the present invention may find other uses, and be adapted therefore.
Levellers take many shapes and designs, including those which are merely dragged along the ground. Many, however, have blades (sometimes known as mould boards) for levelling and altering the contour of the ground. In these versions, the height of the blade is typically able to be altered, which allows the user control over grading, levelling and/or sculpting the contour of the ground. Elevation adjustment is sometimes achieved by raising the entire levelling assembly, while others may rely on merely raising and lowering the portion with the blade. One prior art device uses a central hydraulic actuator to raise and lower the blade portion, which is connected to the main body portion with two dual parallel arm linkages. A wheeled carriage extending from the main body portion helps keep the main body portion at a constant height relative to the ground.
For agricultural applications, generally the contour of the land needs merely to be smoothed. However, levellers have found use in construction sites where they are commonly used to level large areas for foundations, particularly concrete foundations. Here the levelling needs to be precisely, and truly horizontal. Achieving this requires operator skill, and patience. Wheeled versions, such as described above, tend to be most popular as merely raising and lowering the blade (as opposed to the entire leveller assembly) is quicker and more precise, enabling quick responses. When coupled with a laser levelling system, adjusting only the blade elevation allows the operator to work much more quickly.
In many instances, not only must the blade elevation be altered but so too must its inclination relative to the tractor/skid steer to ensure that it is always at true horizontal. If the tractor unit traverses a slope, a fixed inclination blade will level the ground at the same inclination as the tractor unit is. This makes levelling mounds and slopes to the true horizontal extremely difficult.
To address this the prior art uses leveller attachment arrangements (typically the ubiquitous Quick-Hitch) which include an arrangement for varying the inclination of the attachment. These rotational arrangements are expensive, and also add considerable weight to the load carried by the tractor unit. They are also limited in the degree of precision with respect to inclination to a particular angle, and relatively slow to adjust. This slows any levelling operation.
Accordingly, the inventor has identified a need for a levelling unit, which can address the above issues, and at least provide a blade portion able to be adjusted in elevation, and inclination (about a rotational axis substantially the same as the direction of travel), and which can be attached to standard connections such as the Quick Hitch, while avoiding the use of additional rotational assemblies.
In some situations ground preparation work needs to be performed before levelling and grading can occur. In practice this involves working the ground/site with a different implement. For example, where a site is covered with grass or weed, something such as what is commonly known as a “Harley Rake” may be used, which is essentially a powered rotating drum rake. The radially protruding tines on the powered rotating rake penetrate through the upper layer of the ground, to effectively break up thatch, matted plant material, compacted soil, and even light man made surface coverings such as bitumen (depending on the design of the drum). Without this prior treatment the blade tends to skid across the surface of the ground.
In more difficult situations a fixed rake (i.e. not a powered rotating rake) with downward ground penetrating tines may be used to break up harder ground, or where foreign objects which may damage a Harley rake may be present. This solution is more likely to be used on old construction and demolition sites, or where harder man-made coverings of asphalt and bitumen may be present. Again, preparing the ground prior to subsequent operation with a blade assembly allows more effective levelling to be performed.
The problem with the prior art techniques is that the ground must be worked more than once—first with a ground preparing tool, and then the levelling/contouring operation. If the operator has two machines, then one can be preparing the ground while the leveller follows. The disadvantages of these techniques is the extra cost for more tools, the extra time of multiple operations, and the extra cost if more than one tractor is used. To the industry these represent significant disadvantages in terms of time and capital expense. It would therefore be a significant advantage to the ground-working and construction industries if these disadvantages could at least be partially addressed.
Also, more and more operators are using laser guidance systems for controlling their attached implements. The additional speed and accuracy of laser assisted guidance is making it almost a necessity for operators to implement due to remain competitive and meet accelerated timeframe expectations required on many jobs. The downside is that such systems are an expensive investment, and usually they are only implemented on a blade implement, and not on other accessories as well. However, there is still advantage if accessories performing ground preparation work are also able to be controlled by laser guided assistance systems. Apart from reducing the work required by a subsequent blade operation, there are some instances where significant advantage may be obtained.
One such instance is in roadway repair and construction, and by roadway we include paths, sidewalks, carparks, and similar sealed areas. Quite often minimal and subtle grading is required (more for water runoff requirements), and being able to use a laser assisted power rake to prepare sublayers for final application of concrete or asphalt can be advantageous.
It would therefore be of advantage to the roading, groundworking, and construction industries at least, if the additional cost of adding laser guided control systems to individual ground-working accessories could be addressed.
It is also useful for some applications to not only be able to modify the roll characteristics of a blade or accessory, but sometimes also the pitch and/or yaw (using aircraft terminology). This can be dictated by a number of factors, including the terrain and materials being worked, but is sometimes useful. It would therefore be useful if a leveller (and accessory where fitted) could be controlled to provide for adjustments in either or both pitch and roll as well according to user and operator choice.
It is an object of the present invention to address at least some of the above problems.
At the very least it is an object of the present invention to provide the public with a useful alternative choice.
Aspects of the present invention will be described by way of example only and with reference to the ensuing description.